Processes are well known for continuously contacting fluids with solid particles to effect chemical separations by intimately contacting the fluid with solid particles, such as ion exchange resins, by causing the fluid to flow upward in a column counter-current to solid particles moving downward in the column. In such processes, where the solid particles are fluidized there is a tendency for the finer fraction of solid particles to be carried to the upper part of the column where they tend to be held permanently. These fine particles, being partially saturated with the components removed from the fluid stream, result in decreased efficiency in the operation of the process. Use of solid particles having a uniform particle size provides some improvement but due to attrition of the particles during the movements through the circuit there is eventually a build-up of small particles near the top of the column.
Other processes, employing packed beds of absorbent particles also have the disadvantage that, although they can be used with clarified fluids, they are not satisfactory for use with unclarified fluids or turbid liquids primarily because of a build-up of suspended matter on the particles. This results in excessive build-up of pressure in the column. Although this problem can be avoided by prior clarification of the fluid or liquid, it is often desirable to avoid such clarification because of expense involved.
In U.S. Pat. No. 3,207,577 a counter-current ion exchange is disclosed which is carried out in a vessel having a succession of horizontal levels with the resin being washed in a separate vessel and then proceeding to an elution vessel. In U.S. Pat. No. 3,235,488 a washing tank is disclosed which restores fouled anion exchange resins by violent agitation in a confined space with a limited breakdown of the resin particles. U.S. Pat. No. 3,152,072 relates to an ion exchange apparatus in which the resin particles are continuously transferred using liquid pressure with the resin being moved from the ion exchange column into a regenerator, then into a water washing vessel and back to the liquid passing column. A combination of ion exchange and flotation is disclosed in U.S. Pat. No. 3,240,556 with classification and clarification steps being eliminated in a resin-in-pulp process for treating uranium ores. In U.S. Pat. No. 3,551,118 solid-fluid contacting, e.g. ion exchange processes, is disclosed with conical plates disposed on above the other allowing passage of phases from one stage to the next.
None of the foregoing patents discloses the apparatus, and, in particular, the absorption column of the present invention which relates to an improved process and apparatus for continuous counter-current contact between a fluid to be treated and solid particles wherein the fluid flows through a column containing a plurality of contacting chambers each of which contains solid particles and in which intermittent transfer of the particles in a direction opposite to that of the fluid from each chamber to the chamber immediately adjoining is effected while maintaining a continuous flow of the fluid through the column.